It's good that http://effbot.org/tkinterbook/photoimage.htm has the note about having to keep a reference. I found the page after fathoming out what the problem was myself, and therefore knowing what to Google for. Could the note be extended to explain why the reference Tk must be keeping to the image isn't sufficient?
That assumes that I can figure out why Tk behaves that way :-). If I remember correctly, the library does indeed keep the internal image object around, since it's being displayed, but it explicitly clears the content when Tkinter releases it.
It's good that http://effbot.org/tkinterbook/photoimage.htm has the note about having to keep a reference. I found the page after fathoming out what the problem was myself, and therefore knowing what to Google for. Could the note be extended to explain why the reference Tk must be keeping to the image isn't sufficient?
That assumes that I can figure out why Tk behaves that way :-). If I remember correctly, the library does indeed keep the internal image object around, since it's being displayed, but it explicitly clears the content when Tkinter releases it.